\begin{table}%t7
%\centering
\par
\caption{\label{tab:cdn4fluc}Column densities in \pscm ~and molecular fraction $f$ for the dense PDR models in which surface chemistry is cut  for very small grains ($r < 1.0 \times 10^{-6}$ cm). Numbers in parentheses refer to power of ten.}
\small \begin{tabular}{lllllllll}
\hline\hline
Model &  H   &    H$_2$   &  $f$   &   D   &  HD  &  C  & CO  &  CH \\
\hline 
RC$'$    & 5.88(21) & 6.41(21) &  0.69   & 3.52(16)  &   2.43(17)  &  8.45(17) & 1.11(18) & 1.02(15) \\  
MC$'$    & 8.40(21) & 5.16(21) &  0.55   & 3.47(16)  &   2.46(17)  &  9.27(17) & 1.02(18) & 1.06(15) \\
\hline
\end{tabular}
\end{table}